1. Field of the Invention
This invention relates to safety switch assemblies used especially but not exclusively in machinery guards enclosing kinetic machinery.
Known safety switch assemblies comprise a safety switch adapted to be fitted to an enclosure and an actuator adapted to be fitted to a door, gate or protective cover of the enclosure and insertable into the safety switch to turn ON the electrical power supply when the enclosure is closed by the door, gate or protective cover.
2. Description of the Prior Art
Known safety switches comprise within a housing normally-open contacts, one set fixed, and the other movable and carried by an axially-movable push rod spring-loaded to maintain the sets of contacts apart and the power supply consequently OFF.
The axially-movable push rod is connected to a rotatable cam of a cam arrangement normally disposed to prevent cam rotation and consequently to secure the push rod in a power supply OFF position but which is operable by the actuator to cause cam rotation and axial movement of the push rod to a power supply ON position.
Cam arrangements are known in which the rotatable cam prevented from rotating by a releasable connection between the cam and a non-rotatable locking element, rotation of the cam and consequent axial movement of the push rod from the OFF position to the ON position being effected by the actuator engaging the rotatable cam either to move the cam axially along its axis of rotation to release the connection between the rotatable cam and non-rotatable locking element, or to move the latter axially along a shaft defining the axis of rotation of the cam to release the connection with the cam.
These known cam arrangements are vulnerable to loss of free axial movement of the cam or the locking element along the cam shaft due to the accumulation of dust and grease between the latter and the cam or the locking element which may inhibit their axial displacement by the actuator or their return to the locked position upon withdrawal of the actuator.
It is an object of the present invention to provide an improved switch assembly.